1. Field of the Disclosure
The present invention relates to semiconductor devices, and more particularly, to a semiconductor device and a method of manufacturing the same, in which an on-resistance characteristic is maintained and at the same time a breakdown voltage can be improved.
2. Discussion of the Related Art
An example of a power semiconductor device includes a device which is operable at a high voltage, close to a theoretical breakdown voltage of a semiconductor. If an external system which uses a high voltage is controlled by an integrated circuit, the integrated circuit may require a built-in semiconductor device for controlling the high voltage. Namely, the semiconductor device for the high voltage may require a structure that has a high breakdown voltage.
That is, in a drain or a source of a transistor to which the high voltage is directly applied, a punch through voltage between the drain and source and the semiconductor substrate, and the breakdown voltage between the drain and source and a well or substrate may be higher than the high voltage. A lateral diffused MOS (LDMOS) is a semiconductor device for the high voltage.
FIG. 1A and FIG. 1B are cross-sectional views illustrating a general LDMOS transistor. As illustrated in FIG. 1A, the LDMOS transistor includes a high voltage N-well region 110, a device isolation film 120, a P type body 115, a gate oxide film 130, source regions 140 and 150, an N type well region 135, a drain region 145, a gate 160, and a spacer 165.
When the LDMOS transistor is turned off, if a positive voltage is applied to the drain region 145, an electric field is formed below the gate 160. At this time, the electric field is formed most densely at a boundary 125 where one end of the device isolation film 120 and the drain region 145 of high density meet. Accordingly, breakdown occurs at the boundary, thereby limiting a breakdown voltage of the LDMOS transistor.
FIG. 1B illustrates a structure for solving the problem of FIG. 1A. As the distance between the LDMOS transistor and the source region 140 increases, a size of the device increases and a current path becomes long, whereby on-resistance (Ron) characteristic may deteriorate.